Funnel and method of filtering



June 15, 1943. G. ZARBO FUNNEL AND METHOD OF FILTERING Filed Sept. 7,1939 :inucn'fot/ George Zar'b 0,

Patented June 15, 1943 George Zarbo, Vineland, N. J., assignor to KimbleGlass Company, Vineland, N. 3., a corporation of Illinois ApplicationSeptember 7, 1939, Serial No. 293,847 3 Claims. (Q1. 210-160) Thepresent invention relates to conical funnels of the type adapted tosupport filter paper and the method of supporting the filter paper inthe funnel. More particularly the invention relates to a funnel havingan angle of convergence less than that of a filter paper formed orfolded to be supported in the funnel.

One of the common means of filtering a mixture of liquid and solidparticles is to fold a round disc of filter paper twice alongdiametrical lines at right angles to each other and spread it to form acone-shaped filter, this filter then being placed in a funnel, afterwhich the liquid-solid mixture is poured into the supported filter. Whena filter paper is thus folded, the angle of convergence is sixtydegrees, It has been the practice to shape the inner surface of thefunnel so that its angle of convergence is likewise sixty degrees. Hencethe filter paper fits snugly within the funnel, and, except for a smallportion at the apex, extending into the spout of the funnel, is inintimate contact with the inner surface of the funnel at all points.When the paper is wetted, it hugs the wall of the funnel tightly, thusretarding the passage of liquid through the paper and into the stem ofthe funnel.

Various ways of modifying funnels have been proposed to hasten thepassage of liquid through filters. In the so-called fluted funnelslongitudinal ribs and/or channels have been formed on and in the surfaceof the funnel for this purpose. These devices have the effect ofincreasing the speed of filtration, but are objectionable for tworeasons: First, they add to the cost of the funnel; and secondly, whenthe irregularities in the surface are made sufficiently pronounced tohave a marked effect on the speed of filtration, it is then found thatthe paper filter is insufficiently supported and the funnel can nolonger be used with suction. With such a funnel, an attempt to usesuction (with small platinum cone at apex of the funnel) results inrupture of the paper in the fluted area of the funnel.

It is one of the objects of the present invention to form a conicalfunnel, the angle of convergence of the inner surface of which isslightly less than sixty degrees.

It is also an object of this invention to use a funnel whose sidesconverge at less than sixty degrees in combination with the conventionalpaper cone having an angle of convergence of sixty degrees.

It is also an object of the invention to produce a funnel having asmooth inner surface, free from protuberances or channels, this innersurface supporting a substantial portion of a sixtydegree paper cone butleaving another substantial portion of the cone unsupported.

Other objects will be apparent from the following description of theinvention taken in connection with the accompanying drawing, in which:

Fig. 1 is a perspective of a filter paper folded in a conventionalmanner; and

Fig. 2 is a sectional elevation of a preferred form of funnelillustrated as supporting a filter paper folded as in Fig. 1.

In the drawing, it will be seen that the funnel H3 comprises a conicalbody portion H and a stem I2 at the small end thereof. The filter paperI3 is folded in a conventional manner, that is, by first folding along adiametrical line and then doubling the first fold along a seconddiametrical line at right angles to the first fold. When spread, thefolded paper takes the form of a hollow cone, the sides of whichconverge at an angle of sixty degrees. The cone-shaped filter is thenplaced in the funnel ID as shown in Fig. 2 wherein it is supported. Aliquid-solid mixture poured into the filter will be separated into itssolid and liquid phases, the solid phase remaining in the filter whilethe liquid phase passes through the paper and is discharged through thespout l2.

At the present time all funnels made for laboratory use and intended tosupport filter papers folded in the conventional manner herein referredto, have an angle of convergence of sixty degrees, the same as that ofth filter. It will be obvious, assuming the inner surface of the funnelto be smooth, that all of the filter, except the tip or apex l4, liessnugly against the funnel wall.

As illustrated in Fig. 2, the folded filter converges at an angle ofsixty degrees. The present funnel, however, has an angle of convergenceslightly less thansixty degrees. In the drawin this angle is shown asfifty-eight degrees, although it might be slightly more or less. By thussupporting the filter in the funnel, it is apparent that that portion ofthe filter adjacent the apex end of the cone will be spaced, as at 15,from the wall of the funnel for a substantial distance above the apex,this spacing gradually diminishing toward the mouth end I6 of thefilter. The

portion nearest the mouth end of the filter will,

of course, he closely against the wall of the funnel, as indicated at H.It has been found in tests that the rate of filtration in filters thussupported in a funnel is markedly increased. As

examples of actual tests made, the following tables are illustrative ofthe rate of filtering with fluted funnels, plain sixty degree funnelsand plain fifty-eight degree funnels.

Filtration time using 110 m/m Whatman #40 paper Total time required TestPrecipitate Funnel Barium sulphate Calcium oxalate n HQ? vmooo-o assss-wee Aluminum hydroxide cleaned than is a fluted-funnel. Even withsagging thepaper may-have light contact with the wall of the funnel, butit will rest at the points of contact with relatively little pressureagainst the wall so that liquid will readily pass through the filter.

While a preferred angle of convergence, viz., fifty-eight degrees, hasbeen designated as bein effective, this angularity may vary slightlywithout changing the effectiveness of the filter provided, of course,the angularity of the funnel is less than sixty degrees. It is,therefore, intended that the angularity referred to be understood asbeing approximate.

Having described my invention as new, what I claim. and desire to secureby Letters Patent is:

1. Aiunnel having a cone-shaped body portion having a discharge openingat its apex and a wide mouth, the inner surface of the funnel convergingtoward said discharge opening, the angle of convergence beingsubstantially fifty-eight degrees.

2. In combination, a funnel having a coneshaped. body portion having adischarge opening atits apexand a Wide mouth, the'inner surface ofthefunnel converging toward said discharge opening, the angle ofconvergence being substantially fifty-eight degrees, and a cone-shapedfilter element supported in said funnel, the angle of convergence of thesides of the filterbeing sixty degrees.

3. A funnel having a cone-shaped body portionhaving a discharge openingat its-apex and a wide mouth, the inner surfaceof the funnel convergingtoward said discharge opening, the angle of convergence beingsubstantially fiftyeight degrees, said inner surface being whollysmooth.

GEORGE 'ZARBO.

